first =float(input("请输入第一个数:"))
second =float(input("请输入第二个数:"))
operator =input("请选择运算符：+-*/:")
if operator=='+':
    print(first+second)
elif operator=='-':
    print(first-second)
elif operator=='*':
    print(first*second)
elif operator=='/':
    if second==0:
        print("除数不能为0")
    else:
        print(first / second)